The metabolic status of critically ill patients in the intensive care unit (ICU) is of critical importance and needs frequent monitoring. For example, glycemic control in critically ill patients has been shown to positively impact both morbidity and mortality. This has been shown to be true whether the patients have preexisting diabetes or not. Current standards of care for hyperglycemic patients in the intensive care setting involve the use of insulin infusion and monitoring of blood glucose at regular intervals (e.g., once every hour, 24 hours a day).
Metabolic monitoring in most patients is restricted to measuring glucose in blood drawn with a finger prick and then analyzing the sample using commercially available electrochemical glucose monitors, such as the ONETOUCH (LifeScan, Inc., Milpitas, Calif.) or ACCU-CHEK (Roche Diagnostics Corp., Indianapolis, Ind.) systems. Hypoglycemia is the most common complication of using insulin infusion, while also the most limiting and potentially detrimental to patient safety. Yet, the commercially available meters' accuracy decreases significantly at blood glucose levels within the hypoglycemia range (i.e., below 60 mg/dl).
The only metabolic parameter that commercially available glucometers can determine is blood glucose. The monitoring of other fundamental parameters, such as pH, bicarbonate, K+, or lactate is also desirable in a number of situations. Specifically, shifts in potassium between the intracellular and extracellular space are known to occur with insulin therapy. Since sepsis and respiratory failure are common reasons for admission to the ICU, frequent bedside pH measurements are needed and currently performed by arterial blood sampling and blood gas analysis in a central laboratory. This, along with the numerous disposable test strips required for patient care, increases the already high costs of care in the ICU.